Ammonium phosphate is an inorganic salt formed through the chemical reaction between ammonia and phosphoric acid. This compound is highly soluble in water and typically appears as a white, crystalline solid. It is a versatile compound used across various industries, contributing to diverse applications due to its unique chemical composition.
Chemical Makeup and Common Forms
While “ammonium phosphate” is a general term, it primarily refers to two stable, commercially important forms: Monoammonium Phosphate (MAP) and Diammonium Phosphate (DAP). Each form has distinct chemical properties that dictate its specific applications, arising from the varying ratios of ammonia and phosphoric acid used in their production.
Monoammonium Phosphate (MAP) has the chemical formula NH₄H₂PO₄. It contains 11% to 12% nitrogen (N) and 48% to 61% phosphorus pentoxide (P₂O₅). When dissolved in water, MAP solutions are acidic, with a pH between 4.0 and 4.5. This acidic nature influences its suitability for certain agricultural uses.
Diammonium Phosphate (DAP) has the chemical formula (NH₄)₂HPO₄. It contains 18% nitrogen (N) and 46% phosphorus pentoxide (P₂O₅). DAP solutions are alkaline, with a pH ranging from 7.5 to 8. These differing concentrations and pH levels make MAP and DAP suitable for various soil conditions and industrial processes.
Key Applications
Ammonium phosphate finds widespread use, primarily as an agricultural fertilizer. It provides nitrogen and phosphorus, two macronutrients for plant growth. Nitrogen promotes healthy foliage and chlorophyll production, while phosphorus is essential for energy transfer, root development, and flowering processes. Its high water solubility allows for quick dissolution in soil, making nutrients readily available for plant uptake.
Beyond agriculture, ammonium phosphate is used as a fire retardant. It is a component in dry chemical fire extinguishers and flame retardant treatments for materials. When exposed to heat, ammonium phosphate decomposes, releasing non-flammable gases like ammonia and carbon dioxide. This process dilutes combustible gases and oxygen, and promotes a protective char layer on the material’s surface, acting as a physical barrier against heat and oxygen.
It also has food industry applications. It functions as a leavening agent in baking, where heat causes it to evaporate as a gas without residue. It serves as a yeast nutrient in fermentation, such as winemaking. Other industrial uses include pH control and as a flux for soldering metals.